Watching, 'cause I plan on twin 1904's on an Offy manifold in my T-bucket. (Once I get busy and work out the vac advance arrangement.)
Roger
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| Jetting for two Holley single bbl carbs https://www.slantsix.org/forum/viewtopic.php?t=68063 |
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| Author: | Ogilthorpe [ Tue Jan 21, 2025 8:11 am ] |
| Post subject: | Jetting for two Holley single bbl carbs |
I am running an Offy with two single bbl Holleys. My engine is basically stock with the exception of a set of split headers. I am needing some recommendations on jetting. It is currently really rich. |
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| Author: | Dart270 [ Tue Jan 21, 2025 8:29 am ] |
| Post subject: | Re: Jetting for two Holley single bbl carbs |
What jets do you have in there now? Also, have you done a valve lash adjustment recently? Tight valves can really make the car run rich at idle and low speed. This is really important to do. Also also, what are your ignition timing settings? Thanks and all the best, Lou |
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| Author: | Ogilthorpe [ Tue Jan 21, 2025 3:58 pm ] |
| Post subject: | Re: Jetting for two Holley single bbl carbs |
I haven't pulled the carbs yet but will this week. I'll post the current jet size once I get them apart. I will also recheck the valve lash. Thank you for the reply. |
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| Author: | SlantSixDan [ Tue Jan 21, 2025 11:10 pm ] |
| Post subject: | Re: Jetting for two Holley single bbl carbs |
Are you running Holley 1920s, Holley 1945s, something else? Which ones specifically (carb type numbers stamped into the body)? |
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| Author: | Dart270 [ Wed Jan 22, 2025 3:23 am ] |
| Post subject: | Re: Jetting for two Holley single bbl carbs |
Oh yeah, we definitely need to know carb type too... Lou |
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| Author: | GTS225 [ Wed Jan 22, 2025 5:36 am ] | ||
| Post subject: | Re: Jetting for two Holley single bbl carbs | ||
Watching, 'cause I plan on twin 1904's on an Offy manifold in my T-bucket. (Once I get busy and work out the vac advance arrangement.) Roger
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| Author: | Greg Ondayko [ Fri Jan 24, 2025 10:10 am ] |
| Post subject: | Re: Jetting for two Holley single bbl carbs |
Are the Jets for the single barrel Holleys readily available? Maybe they are the same as the four barrel carbs? I had a Carter BBS that seemed like it had a jet and rod combination that was not shared by the WCFB / AFB / AVS/ Edelbrock units. |
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| Author: | Charrlie_S [ Fri Jan 24, 2025 10:21 am ] |
| Post subject: | Re: Jetting for two Holley single bbl carbs |
The Holey 1920 uses the same jets as the common 4 bbl carbs |
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| Author: | Ogilthorpe [ Fri Jan 24, 2025 10:36 am ] |
| Post subject: | Re: Jetting for two Holley single bbl carbs |
Sorry I haven't responded as my wife fell and broke her arm and as a result I've had no time to go pull those carbs. I will get them removed tomorrow and let you know what I find. Thank you for all of your responses. All are appreciated. |
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| Author: | Ogilthorpe [ Sun Feb 02, 2025 11:17 am ] |
| Post subject: | Re: Jetting for two Holley single bbl carbs |
Ok, I finally found time to remove these carbs. (the wife had to have surgery but is ok) They are 1920 Holleys . The jets were 65 which seems like a fire hose nozzle for this motor. Any thoughts on what size to start with? |
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| Author: | SlantSixDan [ Sun Feb 02, 2025 3:12 pm ] |
| Post subject: | Re: Jetting for two Holley single bbl carbs |
"Holley 1920" is a start, but it's not specific enough. Check the type number, which is stamped near the top-front of the carburetor main body, aft of the bowl. It's on the surface facing the sky on pre-1971 carbs, on the surface facing front on '71-up carbs. Check and report the type number for both carbs. 65 is indeed a very large jet for most 1920 configurations. |
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| Author: | Ogilthorpe [ Sun Feb 02, 2025 3:58 pm ] |
| Post subject: | Re: Jetting for two Holley single bbl carbs |
It's front facing and reads: 1322 6260. 1 |
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| Author: | Charrlie_S [ Sun Feb 02, 2025 4:56 pm ] |
| Post subject: | Re: Jetting for two Holley single bbl carbs |
Back in the day, most Holley 1920's for slant six applications that I took apart had jets in the mid 50's |
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| Author: | Dart270 [ Mon Feb 03, 2025 6:48 am ] |
| Post subject: | Re: Jetting for two Holley single bbl carbs |
Yes, way too big. I would put 56 in both carbs and try that. Lou |
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| Author: | Ogilthorpe [ Mon Feb 03, 2025 7:08 am ] |
| Post subject: | Re: Jetting for two Holley single bbl carbs |
Thank you. I'll try that and let you know. |
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